The number of symbols that are preceded by a letter and not followed by a number in the following expression is ______.
A$1%MB#6&NC = 3!OD + KP1
3
2
4
3
1
4
2
The number of symbols that are preceded by a letter and not followed by a number in the following expression is ______.
A$1%MB#6&NC = 3!OD + KP